A circularly polarizing plate has been used in an image display apparatus such as a liquid crystal display apparatus (LCD) or an organic electroluminescence display apparatus (OLED) for the purposes of improving its display characteristics and preventing reflection. The circularly polarizing plate is typically obtained by laminating a polarizer and a retardation film (typically a λ/4 plate) so that the absorption axis of the polarizer and the slow axis of the retardation film may form an angle of 45°. Hitherto, the retardation film has been typically produced by performing uniaxial stretching or biaxial stretching in a longitudinal direction and/or a lateral direction, and hence its slow axis is expressed in the lateral direction (widthwise direction) or longitudinal direction (lengthwise direction) of a raw film in many cases. As a result, in order to produce the circularly polarizing plate, it has been necessary to perform the following. The retardation film is cut so as to form an angle of 45° relative to its lateral direction or longitudinal direction, and the resultant pieces are bonded to the polarizer one by one.
To solve such problem, there has been proposed a technology involving performing stretching in an oblique direction to express the slow axis of the retardation film in the oblique direction. However, any one of the technologies proposed heretofore involves a problem in that the optical characteristics and/or mechanical characteristics of a retardation film to be obtained are uneven, and the problem becomes remarkable particularly in the widthwise direction.